Electro-optic media produced using ink jet printing

ABSTRACT

Ink jet printing can be used in the production of electro-optic displays for (a) forming a layer of a polymer-dispersed electrophoretic medium on a substrate; (b) forming a color electro-optic layer; (c) forming a color filter; and (d) printing electrodes and/or associated conductors on a layer of electro-optic material.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of copending application Ser. No.13/091,307, filed Apr. 21, 2011 (Publication No. 2011/0195629), which isa division of application Ser. No. 11/689,164, filed Mar. 21, 2007(Publication No. 2007/0223079, now U.S. Pat. No. 7,952,790), whichclaims benefit of Provisional Application Ser. No. 60/743,653, filedMar. 22, 2006.

This application is related to:

-   -   (a) U.S. Pat. No. 6,982,178;    -   (b) application Ser. No. 10/605,024 filed Sep. 2, 2003        (Publication No. 2004/0155857, now U.S. Pat. No. 7,561,324); and    -   (c) U.S. Pat. No. 7,110,164, issued Sep. 19, 2006 on application        Ser. No. 10/904,063, filed Oct. 21, 2004, which claims priority        from Application Ser. No. 60/481,553, filed Oct. 24, 2003;        Application Ser. No. 60/481,554, filed Oct. 24, 2003;        Application Ser. No. 60/481,557, filed Oct. 23, 2003;        Application Ser. No. 60/481,564, filed Oct. 27, 2003; and        Application Ser. No. 60/520,226, filed Nov. 14, 2003.

The entire contents of all the aforementioned applications, and of allother United States Patents and published and copending Applicationsmentioned below, are also herein incorporated by reference.

BACKGROUND OF INVENTION

The present invention relates to electro-optic media produced using inkjet printing. This invention is especially, but not exclusively,intended for use in the production of color electro-optic media.

The term “electro-optic”, as applied to a material or a display, is usedherein in its conventional meaning in the imaging art to refer to amaterial having first and second display states differing in at leastone optical property, the material being changed from its first to itssecond display state by application of an electric field to thematerial. Although the optical property is typically color perceptibleto the human eye, it may be another optical property, such as opticaltransmission, reflectance, luminescence or, in the case of displaysintended for machine reading, pseudo-color in the sense of a change inreflectance of electromagnetic wavelengths outside the visible range.

The terms “bistable” and “bistability” are used herein in theirconventional meaning in the art to refer to displays comprising displayelements having first and second display states differing in at leastone optical property, and such that after any given element has beendriven, by means of an addressing pulse of finite duration, to assumeeither its first or second display state, after the addressing pulse hasterminated, that state will persist for at least several times, forexample at least four times, the minimum duration of the addressingpulse required to change the state of the display element. It is shownin U.S. Pat. No. 7,170,670 that some particle-based electrophoreticdisplays capable of gray scale are stable not only in their extremeblack and white states but also in their intermediate gray states, andthe same is true of some other types of electro-optic displays. Thistype of display is properly called “multi-stable” rather than bistable,although for convenience the term “bistable” may be used herein to coverboth bistable and multi-stable displays.

Several types of electro-optic displays are known. One type ofelectro-optic display is a rotating bichromal member type as described,for example, in U.S. Pat. Nos. 5,808,783; 5,777,782; 5,760,761;6,054,071 6,055,091; 6,097,531; 6,128,124; 6,137,467; and 6,147,791(although this type of display is often referred to as a “rotatingbichromal ball” display, the term “rotating bichromal member” ispreferred as more accurate since in some of the patents mentioned abovethe rotating members are not spherical). Such a display uses a largenumber of small bodies (typically spherical or cylindrical) which havetwo or more sections with differing optical characteristics, and aninternal dipole. These bodies are suspended within liquid-filledvacuoles within a matrix, the vacuoles being filled with liquid so thatthe bodies are free to rotate. The appearance of the display is changedby applying an electric field thereto, thus rotating the bodies tovarious positions and varying which of the sections of the bodies isseen through a viewing surface. This type of electro-optic medium istypically bistable.

Another type of electro-optic display uses an electrochromic medium, forexample an electrochromic medium in the form of a nanochromic filmcomprising an electrode formed at least in part from a semi-conductingmetal oxide and a plurality of dye molecules capable of reversible colorchange attached to the electrode; see, for example O'Regan, B., et al.,Nature 1991, 353, 737; and Wood, D., Information Display, 18(3), 24(March 2002). See also Bach, U., et al., Adv. Mater., 2002, 14(11), 845.Nanochromic films of this type are also described, for example, in U.S.Pat. Nos. 6,301,038; 6,870.657; and 6,950,220. This type of medium isalso typically bistable.

Another type of electro-optic display is an electro-wetting displaydeveloped by Philips and described in Hayes, R. A., et al., “Video-SpeedElectronic Paper Based on Electrowetting”, Nature, 425, 383-385 (2003).It is shown in copending application Ser. No. 10/711,802, filed Oct. 6,2004 (Publication No. 2005/0151709), that such electro-wetting displayscan be made bistable.

One type of electro-optic display, which has been the subject of intenseresearch and development for a number of years, is the particle-basedelectrophoretic display, in which a plurality of charged particles movethrough a fluid under the influence of an electric field.Electrophoretic displays can have attributes of good brightness andcontrast, wide viewing angles, state bistability, and low powerconsumption when compared with liquid crystal displays. Nevertheless,problems with the long-term image quality of these displays haveprevented their widespread usage. For example, particles that make upelectrophoretic displays tend to settle, resulting in inadequateservice-life for these displays.

As noted above, electrophoretic media require the presence of a fluid.In most prior art electrophoretic media, this fluid is a liquid, butelectrophoretic media can be produced using gaseous fluids; see, forexample, Kitamura, T., et al., “Electrical toner movement for electronicpaper-like display”, IDW Japan, 2001, Paper HCS1-1, and Yamaguchi, Y.,et al., “Toner display using insulative particles chargedtriboelectrically”, IDW Japan, 2001, Paper AMD4-4). See also U.S. PatentPublication No. 2005/0001810; European Patent Applications 1,462,847;1,482,354; 1,484,635; 1,500,971; 1,501,194; 1,536,271; 1,542,067;1,577,702; 1,577,703; and 1,598,694; and International Applications WO2004/090626; WO 2004/079442; and WO 2004/001498. Such gas-basedelectrophoretic media appear to be susceptible to the same types ofproblems due to particle settling as liquid-based electrophoretic media,when the media are used in an orientation which permits such settling,for example in a sign where the medium is disposed in a vertical plane.Indeed, particle settling appears to be a more serious problem ingas-based electrophoretic media than in liquid-based ones, since thelower viscosity of gaseous suspending fluids as compared with liquidones allows more rapid settling of the electrophoretic particles.

Numerous patents and applications assigned to or in the names of theMassachusetts Institute of Technology (MIT) and E Ink Corporation haverecently been published describing encapsulated electrophoretic media.Such encapsulated media comprise numerous small capsules, each of whichitself comprises an internal phase containing electrophoretically-mobileparticles suspended in a liquid suspending medium, and a capsule wallsurrounding the internal phase. Typically, the capsules are themselvesheld within a polymeric binder to form a coherent layer positionedbetween two electrodes. Encapsulated media of this type are described,for example, in U.S. Pat. Nos. 5,930,026; 5,961,804; 6,017,584;6,067,185; 6,118,426; 6,120,588; 6,120,839; 6,124,851; 6,130,773;6,130,774; 6,172,798; 6,177,921; 6,232,950; 6,249,271; 6,252,564;6,262,706; 6,262,833; 6,300,932; 6,312,304; 6,312,971; 6,323,989;6,327,072; 6,376,828; 6,377,387; 6,392,785; 6,392,786; 6,413,790;6,422,687; 6,445,374; 6,445,489; 6,459,418; 6,473,072; 6,480,182;6,498,114; 6,504,524; 6,506,438; 6,512,354; 6,515,649; 6,518,949;6,521,489; 6,531,997; 6,535,197; 6,538,801; 6,545,291; 6,580,545;6,639,578; 6,652,075; 6,657,772; 6,664,944; 6,680,725; 6,683,333;6,704,133; 6,710,540; 6,721,083; 6,724,519; 6,727,881; 6,738,050;6,750,473; 6,753,999; 6,816,147; 6,819,471; 6,822,782; 6,825,068;6,825,829; 6,825,970; 6,831,769; 6,839,158; 6,842,167; 6,842,279;6,842,657; 6,864,875; 6,865,010; 6,866,760; 6,870,661; 6,900,851;6,922,276; 6,950,200; 6,958,848; 6,967,640; 6,982,178; 6,987,603;6,995,550; 7,002,728; 7,012,600; 7,012,735; 7,023,420; 7,030,412;7,030,854; 7,034,783; 7,038,655; 7,061,663; 7,071,913; 7,075,502;7,075,703; 7,079,305; 7,106,296; 7,109,968; 7,110,163; 7,110,164;7,116,318; 7,116,466; 7,119,759; 7,119,772; 7,148,128; 7,167,155;7,170,670; 7,173,752; 7,176,880; and 7,180,649; and U.S. PatentApplications Publication Nos. 2002/0060321; 2002/0090980; 2003/0011560;2003/0102858; 2003/0151702; 2003/0222315; 2004/0014265; 2004/0075634;2004/0094422; 2004/0105036; 2004/0112750; 2004/0119681; 2004/0136048;2004/0155857; 2004/0180476; 2004/0190114; 2004/0196215; 2004/0226820;2004/0257635; 2004/0263947; 2005/0000813; 2005/0007336; 2005/0012980;2005/0017944; 2005/0018273; 2005/0024353; 2005/0062714; 2005/0067656;2005/0078099; 2005/0099672; 2005/0122284; 2005/0122306; 2005/0122563;2005/0134554; 2005/0146774; 2005/0151709; 2005/0152018; 2005/0152022;2005/0156340; 2005/0168799; 2005/0179642; 2005/0190137; 2005/0212747;2005/0213191; 2005/0219184; 2005/0253777; 2005/0270261; 2005/0280626;2006/0007527; 2006/0024437; 2006/0038772; 2006/0139308; 2006/0139310;2006/0139311; 2006/0176267; 2006/0181492; 2006/0181504; 2006/0194619;2006/0197736; 2006/0197737; 2006/0197738; 2006/0198014; 2006/0202949;and 2006/0209388; and International Applications Publication Nos. WO00/38000; WO 00/36560; WO 00/67110; and WO 01/07961; and EuropeanPatents Nos. 1,099,207 B1; and 1,145,072 B1.

Many of the aforementioned patents and applications recognize that thewalls surrounding the discrete microcapsules in an encapsulatedelectrophoretic medium could be replaced by a continuous phase, thusproducing a so-called polymer-dispersed electrophoretic display, inwhich the electrophoretic medium comprises a plurality of discretedroplets of an electrophoretic fluid and a continuous phase of apolymeric material, and that the discrete droplets of electrophoreticfluid within such a polymer-dispersed electrophoretic display may beregarded as capsules or microcapsules even though no discrete capsulemembrane is associated with each individual droplet; see for example,the aforementioned U.S. Pat. No. 6,866,760. Accordingly, for purposes ofthe present application, such polymer-dispersed electrophoretic mediaare regarded as sub-species of encapsulated electrophoretic media.

A related type of electrophoretic display is a so-called “microcellelectrophoretic display”. In a microcell electrophoretic display, thecharged particles and the fluid are not encapsulated withinmicrocapsules but instead are retained within a plurality of cavitiesformed within a carrier medium, typically a polymeric film. See, forexample, U.S. Pat. Nos. 6,672,921 and 6,788,449, both assigned to SipixImaging, Inc.

Although electrophoretic media are often opaque (since, for example, inmany electrophoretic media, the particles substantially blocktransmission of visible light through the display) and operate in areflective mode, many electrophoretic displays can be made to operate ina so-called “shutter mode” in which one display state is substantiallyopaque and one is light-transmissive. See, for example, theaforementioned U.S. Pat. Nos. 6,130,774 and 6,172,798, and U.S. Pat.Nos. 5,872,552; 6,144,361; 6,271,823; 6,225,971; and 6,184,856.Dielectrophoretic displays, which are similar to electrophoreticdisplays but rely upon variations in electric field strength, canoperate in a similar mode; see U.S. Pat. No. 4,418,346. Other types ofelectro-optic displays may also be capable of operating in shutter mode.

An encapsulated electrophoretic display typically does not suffer fromthe clustering and settling failure mode of traditional electrophoreticdevices and provides further advantages, such as the ability to print orcoat the display on a wide variety of flexible and rigid substrates.(Use of the word “printing” is intended to include all forms of printingand coating, including, but without limitation: pre-metered coatingssuch as patch die coating, slot or extrusion coating, slide or cascadecoating, curtain coating; roll coating such as knife over roll coating,forward and reverse roll coating; gravure coating; dip coating; spraycoating; meniscus coating; spin coating; brush coating; air knifecoating; silk screen printing processes; electrostatic printingprocesses; thermal printing processes; ink jet printing processes;electrophoretic deposition (See US Patent Publication Number2004/0226820); and other similar techniques.) Thus, the resultingdisplay can be flexible. Further, because the display medium can beprinted (using a variety of methods), the display itself can be madeinexpensively.

The aforementioned U.S. Pat. No. 6,982,178 describes a method ofassembling a solid electro-optic display (including an encapsulatedelectrophoretic display) which is well adapted for mass production.Essentially, this patent describes a so-called “front plane laminate”(“FPL”) which comprises, in order, a light-transmissiveelectrically-conductive layer; a layer of a solid electro-optic mediumin electrical contact with the electrically-conductive layer; anadhesive layer; and a release sheet. Typically, the light-transmissiveelectrically-conductive layer will be carried on a light-transmissivesubstrate, which is preferably flexible, in the sense that the substratecan be manually wrapped around a drum (say) 10 inches (254 mm) indiameter without permanent deformation. The term “light-transmissive” isused in this patent and herein to mean that the layer thus designatedtransmits sufficient light to enable an observer, looking through thatlayer, to observe the change in display states of the electro-opticmedium, which will normally be viewed through theelectrically-conductive layer and adjacent substrate (if present); incases where the electro-optic medium displays a change in reflectivityat non-visible wavelengths, the term “light-transmissive” should ofcourse be interpreted to refer to transmission of the relevantnon-visible wavelengths. The substrate will typically be a polymericfilm, and will normally have a thickness in the range of about 1 toabout 25 mil (25 to 634 μm), preferably about 2 to about 10 mil (51 to254 μm). The electrically-conductive layer is conveniently a thin metalor metal oxide layer of, for example, aluminum or ITO, or may be aconductive polymer. Poly(ethylene terephthalate) (PET) films coated withaluminum or ITO are available commercially, for example as “aluminizedMylar” (“Mylar” is a Registered Trade Mark) from E.I. du Pont de Nemours& Company, Wilmington Del., and such commercial materials may be usedwith good results in the front plane laminate.

Assembly of an electro-optic display using such a front plane laminatemay be effected by removing the release sheet from the front planelaminate and contacting the adhesive layer with the backplane underconditions effective to cause the adhesive layer to adhere to thebackplane, thereby securing the adhesive layer, layer of electro-opticmedium and electrically-conductive layer to the backplane. This processis well-adapted to mass production since the front plane laminate may bemass produced, typically using roll-to-roll coating techniques, and thencut into pieces of any size needed for use with specific backplanes.

The aforementioned 2004/0155857 describes a so-called “double releasesheet” which is essentially a simplified version of the front planelaminate of the aforementioned U.S. Pat. No. 6,982,178. One form of thedouble release sheet comprises a layer of a solid electro-optic mediumsandwiched between two adhesive layers, one or both of the adhesivelayers being covered by a release sheet. Another form of the doublerelease sheet comprises a layer of a solid electro-optic mediumsandwiched between two release sheets. Both forms of the double releasefilm are intended for use in a process generally similar to the processfor assembling an electro-optic display from a front plane laminatealready described, but involving two separate laminations; typically, ina first lamination the double release sheet is laminated to a frontelectrode to form a front sub-assembly, and then in a second laminationthe front sub-assembly is laminated to a backplane to form the finaldisplay, although the order of these two laminations could be reversedif desired.

The aforementioned copending application Ser. No. 11/550,114 describes aso-called “inverted front plane laminate”, which is a variant of thefront plane laminate described in the aforementioned U.S. Pat. No.6,982,178. This inverted front plane laminate comprises, in order, atleast one of a light-transmissive protective layer and alight-transmissive electrically-conductive layer; an adhesive layer; alayer of a solid electro-optic medium; and a release sheet. Thisinverted front plane laminate is used to form an electro-optic displayhaving a layer of lamination adhesive between the electro-optic layerand the front electrode or front substrate; a second, typically thinlayer of adhesive may or may not be present between the electro-opticlayer and a backplane. Such electro-optic displays can combine goodresolution with good low temperature performance.

Ink jet printing has certain features which render it especially usefulin the production of electrophoretic media and displays. Ink jetprinting allows for the deposition of several different “inks”simultaneously in controlled patterns Ink jet printing also allows forprecise control of the amount of “ink” deposited in any specific area ofthe display. Accordingly, various processes for using ink jet printingin the production of electrophoretic media and displays have alreadybeen described. For example, International Application Publication No.WO 00/03291 and the corresponding U.S. Patent Publication No.2004/0190114 teach a method of using ink jet deposition of capsules inregistration with electrodes to make a full color display. U.S. Pat. No.6,327,072 describes the use of ink jet printing to fill a microcellelectrophoretic display, including ink jet printing of multipleelectrophoretic media to form a full color display. U.S. Pat. No.5,975,680 describes a method for producing a non-emissive display havinga plurality of pixels on a substrate and the pixels being defined byintersecting electrodes, comprising: (a) providing a plurality ofreservoirs containing fluids including field-driven solid-phaseparticles; (b) providing a print head located in a printing positionhaving at least one nozzle connected to a reservoir; (c) positioning theintersecting electrodes and for producing a signal associated with theposition of the substrate relative to the print head; (d) moving thesubstrate in a first direction to the printing position in response tothe signal; (e) ejecting drops of fluids from the reservoirs in responseto the signal onto the intersecting electrodes on the substrate; (f)providing relative movement in a second direction between the print headand the substrate for fluids to be transferred to subsequentintersecting electrodes; and (g) providing the field-driven solid-phaseparticles in the fluid transferred to the substrate which change opticaldensity in response to an applied electric voltage between theassociated intersecting electrodes to produce the desired opticaldensity in the non-emissive display.

The present invention provides additional processes for the use of inkjet printing in the manufacture of electrophoretic and otherelectro-optic media and displays

SUMMARY OF THE INVENTION

In one aspect, this invention provides a process for forming upon asubstrate a layer of a two phase electrophoretic medium comprising acontinuous phase and a discontinuous phase, the discontinuous phasecomprising a plurality of droplets, each of which comprises a fluid andat least one particle disposed within the fluid and capable of movingthrough the fluid upon application of an electric field to theelectrophoretic medium, the continuous phase comprising a polymericmaterial, the process comprising ink jet printing the electrophoreticmedium on to the substrate.

In such a process, the electrophoretic medium may be ink jet printedwith its continuous phase in a fluid form, and after printing of theelectrophoretic medium, the electrophoretic medium may be subjected toconditions effective to convert the continuous phase to a solid form,thereby forming a coherent layer of the electrophoretic medium on thesubstrate. For example, the continuous phase of the material which isink jet printed may be an oligomer or low molecular weight polymer whichrequires additional polymerization, cross-linking or drying (a termwhich is used herein to include removal of solvents other than water) toconvert it to a solid form which forms the final coherent layer of theelectrophoretic medium on the substrate.

In one form of this process, the electrophoretic medium is applied to abackplane containing at least one pixel electrode. Typically in such aprocess, the substrate comprises at least first and second pixelelectrodes and a first electrophoretic medium is ink jet printed on thefirst pixel electrode and a second electrophoretic medium, having atleast one optical state different from all the optical states of thefirst electrophoretic medium, is ink jet printed on the second pixelelectrode. It is necessary to control the deposition of the variouselectrophoretic media so as to align them with the pixel electrodes, butin some cases it may not be necessary to align a specificelectrophoretic medium with a specific electrode or set of electrodes.For example, consider a backplane on which are deposited three differentencapsulated electrophoretic media having respectively red/white,green/white and blue/white extreme optical states, with each of thethree media being coated on every third column of pixels in atwo-dimensional row/column array of pixels. Provided that the stripes ofeach medium are accurately aligned with the columns of pixels, it is notnecessary that the same medium always be deposited on (say) column 102of pixels; provided that the same medium is deposited on column 102,column 104, column 106 etc., the final assignment of column 102 to be ared, green or blue column can be handled by the drive electronics orsoftware. The deposition of the various electrophoretic medium may besimultaneous or sequential. In a preferred form of the process, thefirst electrophoretic medium is ink jet printed on the first pixelelectrode with its continuous phase in a fluid form, and then subjectedto conditions effective to convert the continuous phase to a solid form,thereby forming a coherent layer of the first electrophoretic medium onthe first pixel electrode, and thereafter the second electrophoreticmedium is ink jet printed on the second pixel electrode. To assist indepositing the electrophoretic media in alignment with the electrodes,the substrate may be provided with at least one fiducial mark and theprinting of the electrophoretic medium may be effected at at least onepredetermined location relative to the at least one fiducial mark.Alternatively, the substrate may be mounted at a predetermined locationon a stage (for example, apertures on the substrate may be engaged withprojections on the stage) and the printing of the electrophoretic mediumbe effected at at least one predetermined location relative to thestage.

In another aspect, this invention provides a process for forming a frontplane laminate having a color filter, which process comprises:

-   -   providing a light-transmissive, electrically-conductive layer;    -   ink jet printing a plurality of areas of colored material on to        the light-transmissive, electrically-conductive layer, the        plurality of areas including areas of at least two different        colors;    -   applying a layer of an electro-optic material over the colored        material;    -   applying a layer of a lamination adhesive over the layer of        electro-optic material; and    -   applying a release sheet over the layer of lamination adhesive.

The colored material which is ink jet printed may be a precursor to thefinal colored material; for example, the material printed may bepolymerized, cross-linked, dried or otherwise treated to form the finalcolored material in the front plane laminate. Thus, the colored materialmay be ink jet printed in a fluid form and thereafter subjected toconditions effective to convert the fluid form to a solid form, therebyforming a coherent layer of the colored material on thelight-transmissive, electrically conductive layer. The areas of coloredmaterial (which are intended to form a color filter and thereby providea color electro-optic display) may be applied simultaneously orsequentially, i.e., the various different colors may all be applied atthe same time or they may be applied one at a time, or, for example, twocolors may be applied together and one applied at a later time. Inparticular, a first colored material may be ink jet printed in a fluidform, and thereafter subjected to conditions effective to convert thefluid form to a solid form, thereby forming a coherent layer of thefirst colored material, and thereafter a second colored material may beink jet printed on the light-transmissive, electrically-conductivelayer. Since the colored areas in the front plane laminate are intendedto be aligned with multiple sets of electrodes on a backplane when thefront plane laminate is used to form an electro-optic display, it may beconvenient for the ink jet printing operation to print at least onefiducial mark on the light-transmissive, electrically-conductive layerat at least one predetermined location relative to at least one area ofcolored material. These fiducial marks can be used to align the coloredareas with the electrodes in a later stage of the process for forming anelectro-optic display.

In another aspect, this invention provides a process for forming a colorfront plane laminate, which process comprises:

-   -   (a) providing a light-transmissive, electrically-conductive        layer;    -   (b) ink jet printing a plurality of areas of electro-optic        material on to the light-transmissive, electrically-conductive        layer, the plurality of areas including areas of at least first        and second types of electro-optic material, the second type of        electro-optic material having at least one optical state        different from all the optical states of the first type of        electro-optic material;    -   (c) applying a layer of a lamination adhesive; and    -   (d) applying a release sheet over the layer of lamination        adhesive,    -   wherein steps (b) and (c) can be formed in either order.

As noted above, in this process steps (b) and (c) can be formed ineither order. When step (b) is performed before step (c), the pluralityof areas of electro-optic material are ink jet printed on to thelight-transmissive, electrically-conductive layer, and the laminationadhesive is applied to the plurality of areas of electro-optic material;this variant of the process produces a “classic” front plane laminate asdescribed in the aforementioned U.S. Pat. No. 6,982,178. Alternatively,if step (c) is performed before step (b) so that the lamination adhesiveis applied to the light-transmissive, electrically-conductive layer, andthe plurality of areas of electro-optic material are ink jet printed onto the lamination adhesive, the process produces a so-called “inverted”front plane laminate as described in copending application Ser. No.11/550,114, filed Oct. 17, 2006. In the latter variant of the process,after the plurality of areas of electro-optic material have been ink jetprinted on to the lamination adhesive, a second layer of laminationadhesive may be applied to the plurality of areas of electro-opticmaterial. In either variant of the process, as in other processes of theinvention previously described, the electro-optic material may be inkjet printed in a fluid form, and thereafter subjected to conditionseffective to convert the fluid form to a solid form, thereby forming acoherent layer of the electro-optic material on the light-transmissive,electrically-conductive layer. In particular, a first colored materialmay be ink jet printed in a fluid form, and thereafter subjected toconditions effective to convert the fluid form to a solid form, therebyforming a coherent layer of the first colored material, and thereafter asecond colored material is ink jet printed. The process may furthercomprise ink jet printing at least one fiducial mark at at least onepredetermined location relative to at least one area of electro-opticmaterial.

Processes similar to those described above can be used to produce colordouble release films as described in the aforementioned 2004/0155857.Accordingly, this invention provides a process for forming a colordouble release film, which process comprises:

-   -   (a) providing a first release sheet;    -   (b) applying a first layer of a lamination adhesive to the        release sheet;    -   (c) ink jet printing a plurality of areas of colored material,        the plurality of areas of colored material including areas of at        least two different colors;    -   (d) forming a layer of electro-optic material; and    -   (e) providing a second layer of a lamination adhesive and a        second release sheet over the layer of electro-optic material,    -   wherein steps (c) and (d) are performed in either order. Since a        double release film is essentially symmetric, the printing of        the colored, non-electro-optic material may precede or follow        the deposition of the electro-optic material itself, although        when the double release film is used to form an electro-optic        display, it will normally be necessary to ensure that colored        layers (color filter) lie between the electro-optic material and        the viewing surface of the display if the electro-optic material        is of a type which is reflective and essentially opaque.

In this process, step (e) may be effected by forming the second layer oflamination adhesive on the second release sheet and thereafterlaminating the second layer of lamination adhesive and the secondrelease sheet to the remaining layers of the double release film.

The processes described above can also be modified for use in“one-layer-at-a-time” assembly processes as described in theaforementioned U.S. Pat. No. 7,110,164 and copending application Ser.No. 11/307,297, filed Jan. 31, 2006, and Ser. No. 11/682,409, filed Mar.6, 2007. Thus, this invention further provides a process for producingan electro-optic display, which process comprises:

-   -   (a) providing a first release sheet;    -   (b) applying a first layer of a lamination adhesive to the        release sheet;    -   (c) ink jet printing a plurality of areas of electro-optic        material on to the first layer of lamination adhesive, the        plurality of areas including areas of at least first and second        types of electro-optic material, the second type of        electro-optic material having at least one optical state        different from all the optical states of the first type of        electro-optic material; and    -   (d) providing a second layer of a lamination adhesive and a        second release sheet over the layer of electro-optic material.

In this process, step (d) may be effected by forming the second layer oflamination adhesive on the second release sheet and thereafterlaminating the second layer of lamination adhesive and the secondrelease sheet to the remaining layers of the double release film.

This invention also provides another similar process for producing alaminate for use in the production of an electro-optic display, theprocess comprising:

-   -   (a) providing a first release sheet;    -   (b) ink jet printing a plurality of areas of colored material on        to the first release sheet, the plurality of areas including        areas of at least two different colors, thereby forming a first        sub-assembly;    -   (c) providing a second release sheet;    -   (d) forming a layer of electro-optic material on the second        release sheet, thereby forming a second sub-assembly; and    -   (e) laminating the first and second sub-assemblies together with        the areas of colored material in contact with the layer of        electro-optic material to form the laminate.

This process may further comprise forming a layer of a laminationadhesive on a third release sheet, removing one of the first and secondrelease sheets from the laminate produced in step (e), and contactingthe layer of lamination adhesive with one of the plurality of areas ofcolored material and the layer of electro-optic material exposed byremoval of the release sheet.

This invention also provides another similar process for producing alaminate for use in the production of an electro-optic display, theprocess comprising:

-   -   (a) providing a first release sheet;    -   (b) ink jet printing a plurality of areas of electro-optic        material on to the first layer of lamination adhesive, the        plurality of areas including areas of at least first and second        types of electro-optic material, the second type of        electro-optic material having at least one optical state        different from all the optical states of the first type of        electro-optic material, thereby forming a first sub-assembly;    -   (c) providing a second release sheet;    -   (d) forming a layer of a lamination adhesive on the second        release sheet, thereby forming a second sub-assembly; and    -   (e) laminating the first and second sub-assemblies together with        the layer of lamination adhesive in contact with the plurality        of areas of electro-optic material to form the laminate.

This process may further comprise forming a layer of a laminationadhesive on a third release sheet, removing the first release sheet fromthe laminate produced in step (e), and contacting the layer oflamination adhesive with the layer of electro-optic material exposed byremoval of the first release sheet.

In all of these processes, additional layers can be further laminated asdesired.

This invention also extends to processes in which electro-opticmaterials are applied to a backplane containing at least one pixelelectrode. Conveniently, in such a process, first and second types ofelectro-optic materials (the second type of electro-optic materialhaving at least one optical state different from all the optical statesof the first type of electro-optic material) are deposited sequentiallyon the backplane. It is necessary to control the deposition of thevarious electro-optic materials so as to align them with the pixelelectrodes, but in some cases it may not be necessary to align aspecific electro-optic material with a specific set of electrodes. Forexample, consider a backplane on which are deposited three differentencapsulated electrophoretic media having respectively red/white,green/white and blue/white extreme optical states, with each of thethree media being coated on every third column of pixels in atwo-dimensional row/column array of pixels. Provided that the stripes ofeach medium are accurately aligned with the columns of pixels, it is notnecessary that the same medium always be deposited on (say) column 102of pixels; provided that the same medium is deposited on column 102,column 104, column 106 etc., the final assignment of column 102 to be ared, green or blue column can be handled by the drive electronics orsoftware.

As in some of the processes described above, in the process described inthe preceding paragraph, the electro-optic material which is ink jetprinted may be a precursor to the final material; for example, thematerial printed may be polymerized, cross-linked, dried or otherwisetreated to form the final colored material in the front plane laminate.Specifically, when the electro-optic material comprises a plurality ofdroplets of an internal phase (itself comprising electrophoreticparticles in a fluid) dispersed in a binder (whether a capsule wall isor is not present between each droplet and the binder), the materialwill normally be ink jet printed with the binder in a fluid form, andthe binder will thereafter be treated by drying, cross-linking,polymerization etc. to render it into a solid form which binds thedroplets into a mechanically coherent layer. In most cases, it may beconvenient to deposit the first electro-optic material, effect thenecessary treatment of the binder to form mechanically coherent stripesof the first electro-optic material on the backplane, then deposit thesecond electro-optic material, and repeat this sequence until all theelectro-optic materials have been deposited and treated.

It should be noted that, when depositing electro-optic material on abackplane, although it is necessary to deposit the material inregistration with the pixels of the backplane, it may not be necessaryto determine the positions of those pixels directly. In some cases, forexample where polymeric electrodes are employed, such direct observationmay be difficult. For example, it may be possible to provide thebackplane with fiducial marks in known locations relative to the pixelsand electrodes, and deposit the electro-optic material in registrationwith the fiducial marks. Alternatively, the backplane may be held at aknown location relative to a stage or similar support and the positionof the print head (or similar device) used to deposit the electro-opticmaterial controlled relative to the stage. For example, a backplanecould be provided with apertures at predetermined locations and theseapertures engaged with projections on a stage, thus holding thebackplane electrodes at known locations relative to the stage.

Another aspect of the present invention relates to ink jet printing ofedge seals for electro-optic displays. As described, for example, in theaforementioned U.S. Pat. No. 6,982,178, it is often necessary to sealelectro-optic materials from the environment; for example, manyelectro-optic materials are sensitive to moisture. Typically, theelectro-optic material is sandwiched between a backplane and a frontsubstrate; the latter provides mechanical support and protection for thefront electrode of the display. Most of the sealing of the electro-opticmaterial is provided by the backplane and the front substrate, but it isnormally necessary to form an edge seal extending between the frontsubstrate and the backplane to complete the sealing of the electro-opticmaterial. Such an edge seal may be formed by injecting (for example, viaa syringe) an edge sealing material into the gap between the frontsubstrate and the backplane, and curing the edge sealing material, butink jet printing may provide a convenient alternative.

Thus, this invention also provides a process for forming anelectro-optic display, which process comprises:

-   -   providing a front plane laminate comprising a front substrate, a        light-transmissive electrically-conductive layer, and a layer of        electro-optic material;    -   providing a backplane comprising at least one pixel electrode;        and    -   laminating the front plane laminate to the backplane,    -   wherein an adhesive material is ink jet printed on to a        peripheral portion of at least one of the front substrate and        the backplane prior to the lamination, the adhesive material        forming an edge seal sealing the electro-optic material from the        outside environment after the lamination.

This invention also provides another similar process for forming anelectro-optic display, which process comprises:

-   -   providing a backplane comprising at least one pixel electrode;    -   ink jet printing an adhesive material on to a peripheral portion        of the backplane;    -   disposing on a central portion of the backplane lying within the        adhesive material a front plane laminate comprising a front        substrate, a light-transmissive electrically-conductive layer,        and a layer of electro-optic material; and    -   disposing at least one protective layer over the front plane        laminate, the at least one protective layer extending beyond the        periphery of the front plane laminate and contacting the        adhesive material, thereby forming an edge seal around the front        plane laminate.

The edge sealing material may of course be further treated after theedge seal has been formed; for example the edge sealing material may betreated with heat or radiation to effect any necessary curing of theedge sealing material. There are numerous possible ways of forming theedge seal. For example, as illustrated in FIG. 20 of the aforementionedU.S. Pat. No. 6,982,178, it may be desirable to provide one or moreadditional protective layers on the side of the front substrate remotefrom the backplane, and the edge seal may extend from the backplane tothese protective layers rather than to the front substrate itself, sothat the sequence of steps would be (a) ink jet print edge sealingmaterial on peripheral portion of backplane; (b) laminate front planelaminate to backplane so that front plane laminate lies entirely withinedge sealing material; and (c) place one or more protective layers onfront substrate so that protective layers contact edge sealing material,thereby forming an edge seal. The edge sealing material may of course befurther treated after the placement of the protective layers, forexample by heat or radiation to effect any necessary curing of the edgesealing material.

A further aspect of the invention relates to the ink jet printing ofelectrodes and/or conductors on to a layer of electro-optic material.Although as discussed above, in most cases it is common practice to forman electro-optic display by laminating a layer of electro-optic materialto a backplane containing one or more electrodes, there are certaintypes of display where it may be advantageous to form the electrodesdirectly on to the electro-optic material. For example, it is known touse direct drive electro-optic displays (displays in which each pixel,which is typically of substantial size, is provided with a separateconductor which can be used to control the voltage applied to the pixel)as “animated” advertising signs in which the voltages on the pixels arecontrolled so that the sign cycles through a series of differingappearances. Each type of direct drive sign requires a differentarrangement of pixels and hence of pixel electrodes, and if the pixelelectrodes are produced in the conventional manner by etching a layer ofmetal on a backplane, each type of direct drive sign requires thepreparation of at least one mask. Similarly, if the pixel electrodes areprinted by conventional processes, for example using a printing roller,each type of direct drive sign requires the preparation of a new roller.The need for such masks or rollers increases the cost and the productionlead time of direct drive signs. Ink jet printing of pixel electrodesand/or associated conductors directly on to a layer of electro-opticmaterial avoids the need to prepare masks or printing rollers, and thusdecreases costs and production lead time, since the ink jet printing canbe directly controlled by a computer storing an image of the desiredpattern of electrodes and/or conductors; in effect, the ink jet printingprocess uses a virtual, electronic mask rather than a physical one.

Thus, this invention provides a process for forming an electro-opticdisplay, which process comprises forming a layer of an electro-opticmaterial on a substrate, and ink jet printing at least one pixelelectrode or conductor on to the electro-optic material on thesubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1E of the accompanying drawings are schematic sideelevations showing various stages in the production of an active matrixelectro-optic display of the present invention.

FIGS. 2A to 2E are schematic side elevations showing various stages inthe production of a colored front plane laminate of the presentinvention.

FIGS. 3A to 3F are schematic side elevations showing various stages inthe production of a double release film of the present invention.

The accompanying drawings are intended to illustrate the principle ofthe present invention and are not strictly to scale. In particular, thethicknesses of the various layers in the illustrated structures areexaggerated relative to the lateral extent of these layers.

DETAILED DESCRIPTION

As already mentioned, the present invention provides numerous differentprocesses in which ink jet printing is used in the production ofelectro-optic displays and components of such displays, especially frontplane laminates and double release films. However, the numerousdifferent processes of the invention all make use of one of thefollowing four steps:

-   -   (a) ink jet printing a layer of a polymer-dispersed        electrophoretic medium on a substrate;    -   (b) ink jet printing a plurality of different electro-optic        media on a substrate to form a “color” electro-optic layer (in        the sense of an electro-optic layer in which different areas        react differently to application of an electric field);    -   (c) ink jet printing a plurality of different colored materials        on a substrate to produce a color filter (which is not        necessarily a full color filter); and    -   (d) ink jet printing electrodes and/or associated conductors on        a layer of electro-optic material.

Various processes of the present invention will be discussed separatelybelow, but it should be recognized that a single physical display maymake use of more than one aspect of the present invention; for example,a single display might be produced by ink jet printing a plurality ofdifferent electro-optic media on a substrate, and subsequently ink jetprinting electrodes and/or associated conductors on the electro-opticlayer thus produced. In all cases, following the ink jet printing, itmay be necessary or desirable to treat the printed material by drying,polymerization or cross-linking to convert the printed material to acoherent layer on the substrate. In the case of ink jet printing of“colored” materials intended to form a color filter, we do not excludethe possibility that the material as printed might be colorless, or havea color different from its final form, and that the material may need tobe treated, for example by heating or by exposure to an acid or base,after printing in order to produce the final desired color in theprinted material.

In all aspects of the present invention, in principle any known type ofink jet printing may be used. However, when printing electro-optic andespecially electrophoretic media, typically it may be advantageous touse a mechanical (e.g., piezoelectric) ink jet print apparatus ratherthan a thermal apparatus, since exposure of droplets of electrophoreticfluid or exposure of capsules to a thermal print head may cause unwantedchanges in the electrophoretic material, for example by causingconversion of the fluid to gas, or rupture of capsule walls.

As is well known to those skilled in ink jet printing, careful controlof the viscosity of the medium being printed is typically necessary toachieve successful printing. The viscosities of binders used inelectrophoretic materials are typically considerably higher that thoseof normal ink jet printing inks, and it may thus be desirable, when aprocess of the present invention requires printing of an electrophoreticmedium, to lower the viscosity of the binder used, for example byaddition of cosolvents which can be removed by evaporation after theelectrophoretic material has been ink jet printed.

As already mentioned, one aspect of the present invention relates to aprocess for forming a layer of an electrophoretic medium upon asubstrate by ink jet printing of the medium, wherein the medium is apolymer dispersed electrophoretic medium comprising a plurality ofdiscrete droplets of an electrophoretic fluid and a continuous phase ofa polymer binder, or a precursor of such a polymeric material. It isconsidered that, for purposes of ink jet printing, polymer dispersedelectrophoretic media will generally have advantages over bothunencapsulated electrophoretic media (in which a single phase is presentand the electrophoretic particles are free to move through theelectrophoretic medium) and conventional encapsulated electrophoreticmedia (the term “conventional encapsulated electrophoretic media” beingused to refer to media in which a discrete capsule wall surrounds eachdroplet of electrophoretic fluid). In unencapsulated media, theelectrophoretic particles may tend to separate from the surroundingfluid if the medium is left to stand for a substantial period, forexample when the electrophoretic medium is stored for a period ofseveral hours in the reservoir of an ink jet printer. The fluids used inelectrophoretic media are typically volatile hydrocarbons, so there is arisk of a substantial amount of fluid evaporating from the printeddroplets before the electrophoretic fluid is sealed in the finaldisplay. Finally, there is a risk of unencapsulated media spreading orsmearing when the substrate on which the fluid has been applied islaminated to another part of the final display. Polymer dispersedelectrophoretic media do not suffer from any of these disadvantages.Since the electrophoretic fluid is present as a series of discretedroplets, the particles do not leave the droplets in which they areoriginally confined. The continuous phase essentially preventsevaporation of the fluid and, since the continuous phase is formed intoa polymeric layer before lamination of the electrophoretic medium, thecontinuous phase prevents spreading or smearing of the electrophoreticfluid. Conventional encapsulated electrophoretic media possessadvantages similar to polymer dispersed media but, because of thedifferences in physical properties between the electrophoretic fluid andthe capsule wall, in some cases there may be a risk of capsule wallrupture during ink jet printing of the electrophoretic material, withadverse effects upon the electro-optic performance of the final display.Such problems are less likely to occur with polymer-dispersedelectrophoretic media, since an uncured polymer dispersedelectrophoretic medium is essentially a fluid-in-fluid emulsion.

Other aspects of the present invention make use of ink jet printing ofmultiple types of electro-optic media to produce color displays. Oneprocess of this type is illustrated in FIGS. 1A-1E. FIG. 1A illustrates,in a highly schematic matter, a portion of an active matrix backplane(generally designated 100) having three adjacent columns of pixelelectrodes 102, 104 and 106, these columns extending perpendicular tothe plane of FIG. 1A so that only one pixel electrode in each column isvisible in FIG. 1A. (The spacing between the pixel electrodes isexaggerated in FIGS. 1A-1E for ease of illustration.) In a first step ofthe process, as illustrated in FIG. 1B, a first electro-optic medium 108is ink jet printed over the pixel electrodes 102; this firstelectro-optic medium is (for example) a polymer-dispersedelectrophoretic medium having white and red extreme optical states. Thefirst electro-optic medium 108 is applied with its continuous phase in afluid form and is thereafter dried to form a coherent layer ofelectrophoretic medium adhered to the backplane 100. In the next step ofthe process, as illustrated in FIG. 1C, a second electro-optic medium110 is ink jet printed over the pixel electrodes 104; this secondelectro-optic medium is (for example) a polymer-dispersedelectrophoretic medium having white and green extreme optical states.The second electro-optic medium 110 is applied with its continuous phasein a fluid form and is thereafter dried to form a coherent layer ofelectrophoretic medium adhered to the backplane 100. Similarly, asillustrated in FIG. 1D, a third electro-optic medium 112 is then ink jetprinted over the pixel electrodes 106; this third electro-optic mediumis (for example) a polymer-dispersed electrophoretic medium having whiteand blue extreme optical states. The third electro-optic medium 112 isapplied with its continuous phase in a fluid form and is thereafterdried to form a coherent layer of electrophoretic medium adhered to thebackplane 100.

Separately, an adhesive layer 114 is coated on to a film comprising apolymeric layer 116 (which may, for example, be formed of poly(ethyleneterephthalate) (PET)) bearing on one surface a layer 118 ofindium-tin-oxide (ITO). The resultant adhesive layer/polymeric filmsub-assembly is then laminated to the structure shown in FIG. 1D, withthe adhesive layer 114 in contact with the electrophoretic media 108,110, 112 to produce the final display shown in the FIG. 1E.

It will readily be apparent that numerous variations are possible in theprocess shown in FIGS. 1A-1E. For example, the adhesive layer 114 couldbe applied over the cured electrophoretic media 108, 110, 112 and thefilm 116, 118 laminated to the adhesive present on the backplane.Provided that the electrophoretic media can be printed with gaps betweenthem, or formulated in such a manner that they do not mix, the threeelectrophoretic media could be printed and cured simultaneously ratherthan sequentially as described above. In some cases, it may beconvenient to print the electrophoretic media 108, 110, 112 on to arelease sheet (not shown in the drawings) rather than directly on to thebackplane 100, and then to laminate the printed electrophoretic media onto the backplane and remove the release sheet. Printing theelectrophoretic media on to a smooth release sheet in this mannerprovides electrophoretic media with a very smooth surface remote fromthe backplane and may facilitate lamination of the electrophoretic mediato the adhesive layer.

FIGS. 2A-2E illustrate a process of the present invention for productionof a colored front plane laminate. The process begins (as shown in FIG.2A) with a PET film 216 bearing an ITO layer 218. In a first step of theprocess, as illustrated in FIG. 2B, a first electro-optic medium 208 isink jet printed in stripes over substantially one-third of the ITO layer218; this first electro-optic medium is (for example) an encapsulatedelectrophoretic medium having white and red extreme optical states. Thefirst electro-optic medium 208 is applied with its binder in a fluidform and is thereafter dried to form a coherent layer of electrophoreticmedium adhered to the ITO layer 218. In the next step of the process, asillustrated in FIG. 2C, a second electro-optic medium 210 is ink jetprinted in stripes adjacent and parallel to the stripes of the firstelectro-optic medium 208 on to the ITO layer 218; this secondelectro-optic medium is (for example) an encapsulated electrophoreticmedium having white and green extreme optical states. The secondelectro-optic medium 210 is applied with its binder in a fluid form andis thereafter dried to form a coherent layer of electrophoretic mediumadhered to the ITO layer 218. Similarly, as illustrated in FIG. 2D, athird electro-optic medium 212 is then ink jet printed in stripesadjacent and parallel to the stripes of the first and electro-opticmedia 208 and 210 on to the ITO layer 218; this third electro-opticmedium is (for example) an encapsulated electrophoretic medium havingwhite and blue extreme optical states. The third electro-optic medium212 is applied with its binder in a fluid form and is thereafter driedto form a coherent layer of electrophoretic medium adhered to the ITOlayer 218.

Separately, an adhesive layer 214 is coated on to a release film 216.The resultant adhesive layer/polymeric film sub-assembly 214, 216 isthen laminated to the structure shown in FIG. 2D, with the adhesivelayer 114 is contact with the electrophoretic media 208, 210, 212 toproduce the final front plane laminate shown in FIG. 2E.

As already mentioned, a second aspect of the present invention relatesto providing a color filter by ink jet printing a plurality of areas ofcolored material on to a substrate, the plurality of areas includingareas of at least two different colors. In such a process, there willtypically be areas of at least three, and possibly four, differentcolors, for example, red/green/blue, red/green/blue/white oryellow/cyan/magenta, in order that the color filter can eventually beused to produce a full color display. White areas, if present, can ofcourse be provided simply by not coating a colored material over therelevant areas of the conductive layer. Conveniently, the variouscolored areas are in the form of parallel stripes, or, in the case offour color filters, in the form of multiple 2×2 arrays of colored areas.

A wide variety of colored materials may be used in such process. Forexample, the colored material may be a hard coat material. We do notexclude the possibility that the colored material could serve functionsin addition to acting as a color filter; for example, the coloredmaterial could serve as an adhesive to improve adhesion of theelectro-optic material to the substrate, or might act as a barrier layerto prevent environmental contaminants, such as moisture, or radiationreaching the electro-optic material Ink jet printing of colored materialin accordance with the present invention can provide a totally polymericcolor filter array which may be very useful in the construction offlexible or conformal electro-optic displays.

FIGS. 3A-3F illustrate a process for the production of a color doublerelease film or inverted front plane laminate in which a color filter isprovided by ink jet printing in accordance with the present invention.Some steps of this process also make use of the “one-layer-at-a-time”construction techniques of the aforementioned U.S. Pat. No. 7,110,164.

In the first step of this process, as shown in FIG. 3A, a coloredmaterial 302, which may be for example a solution of a red dye ornanoparticle pigment in a curable resin, is deposited in the form ofspaced stripes on a first release sheet 300. The colored material 302 isthen cured to form a coherent layer of the colored material 302 on therelease sheet 300. As shown in FIGS. 3B and 3C, the process step isrepeated successively with green and blue colored materials 304 and 306to form an RGB filter layer on the release sheet 300. Next, as shown inFIG. 3D, a layer of electro-optic material 308 is then deposited overthe colored materials 302, 304, 306; this layer of electro-opticmaterial 308 may be, for example, a layer of a polymer-dispersedelectrophoretic material deposited by ink jet printed, or a layer ofencapsulated electrophoretic material deposited by slot coating or othermeans. Typically, after deposition it is necessary to dry or otherwisecure the electro-optic material 308 to form this material into acoherent layer.

Separately, a thin layer of lamination adhesive 310 is deposited on asecond release sheet 312 and dried. The dried lamination adhesive 310 isthen laminated, typically under heat and pressure, to the exposedsurface of the electro-optic material 308, to form the structure shownin FIG. 3E, which is itself a double release film as described in theaforementioned 2004/0155857.

In the final step of the process, a thick layer of lamination adhesive314 is deposited on a third release sheet 316 and dried. The firstrelease sheet 300 is removed from the structure of FIG. 3E (as willreadily be apparent to those skilled in the use of release sheets, it isnecessary to choose the first and second release sheet carefully toensure that the removal of the first release sheet 300 from thestructure of FIG. 3E can be achieved without damaging the underlyingcolor filter layer and without disturbing the second release sheet 312),and the dried lamination adhesive 314 is then laminated, typically underheat and pressure, to the exposed surface of the color filter layer 302,304, 306, to form the structure shown in FIG. 3F, which is an invertedfront plane laminate as described above.

Finally, as already noted, another aspect of the present inventionrelates to ink jet printing of electrodes and/or conductors on to alayer of electro-optic material. Suitable materials for ink jet printingof electrodes and conductors are available commercially, for exampleprinting ink AG-II-G-100 S1, sold by Cabot Corporation of Billerica,Mass. Printing of electrodes and conductors directly on to a layer ofelectro-optic material in accordance with the present invention may beused to form a modified front plane laminate, inverted front planelaminate or double release film with electrodes and conductors alreadyin place, such that the front plane laminate etc. can be laminateddirected to a “backplane” provided with a minimal number of contact padswhich contact conductors provided on the front plane laminate.Furthermore, the use of such a modified front plane laminate may enablea single standardized backplane with a standard arrangement of contactpads (for example, a row of contact pads along one edge of thebackplane) to be used with a large number of different modified frontplane laminates.

Two potential problems with printing conductors directly on toelectro-optic material are that the shapes of the conductors will bevisible on the final image (since the conductors are at the same voltageas their associated electrodes, the conductors will also switch theelectro-optic material) and that, with some arrangements of electrodes,it may be difficult to arrange for conductors to reach a desiredlocation, for example a contact pad at the edge of the display, withoutcrossing other conductors or electrodes. Both these problems may bereduced or overcome by ink jet (or otherwise) printing a layer of adielectric material between the electro-optic material and theconductors, or between intersecting conductors and intersectingconductors and electrodes. In the case where two conductors need tocross, it may be desirable to use two separate dielectric layers, thusproducing an electro-opticmaterial/dielectric/conductor/dielectric/conductor structure.

Numerous changes and modifications can be made in the preferredembodiments of the present invention already described without departingfrom the scope of the invention. Accordingly, the foregoing descriptionis to be construed in an illustrative and not in a limitative sense.

1. An article of manufacture comprising, in order: (a) alight-transmissive, electrically-conductive layer; (b) a plurality ofareas of colored material ink jet printed on to the light-transmissive,electrically-conductive layer, the plurality of areas including areas ofat least two different colors; (c) a layer of an electro-optic material;(d) a layer of a lamination adhesive; and (e) a release sheet.
 2. Anarticle of manufacture according to claim 1 wherein the colored materialis ink jet printed in a fluid form, and is thereafter subjected toconditions effective to convert the fluid form to a solid form, therebyforming a coherent layer of the colored material on thelight-transmissive, electrically-conductive layer.
 3. An article ofmanufacture according to claim 2 wherein a first colored material is inkjet printed in a fluid form, and is thereafter subjected to conditionseffective to convert the fluid form to a solid form, thereby forming acoherent layer of the first colored material, and thereafter a secondcolored material is ink jet printed on the light-transmissive,electrically-conductive layer.
 4. An article of manufacture according toclaim 1 further comprising at least one fiducial mark ink jet printed onthe light-transmissive, electrically-conductive layer at at least onepredetermined location relative to at least one area of coloredmaterial.
 5. An article of manufacture, comprising, in order: (a) afirst release sheet; (b) a first layer of a lamination adhesive; (c) aplurality of areas of colored material ink jet printed on the previouslayer, the plurality of areas of colored material including areas of atleast two different colors; (d) a layer of electro-optic material; (e) asecond layer of a lamination adhesive; and (f) a second release sheet,wherein layers (c) and (d) are in either order.
 6. An article ofmanufacture according to claim 5 wherein the plurality of areas ofcolored material are ink jet printed on to the first layer of laminationadhesive.
 7. An article of manufacture according to claim 5 wherein theplurality of areas of colored material are ink jet printed on to thelayer of electro-optic material.
 8. An article of manufacture accordingto claim 5 wherein at least one of the plurality of areas of coloredmaterial is ink jet printed in a fluid form, and is thereafter subjectedto conditions effective to convert the fluid form to a solid form,thereby forming a coherent area of the colored material.
 9. An articleof manufacture according to claim 8 wherein a first colored material isink jet printed in a fluid form, and is thereafter subjected toconditions effective to convert the fluid form to a solid form, therebyforming a coherent area of the first colored material, and thereafter asecond colored material is ink jet printed.
 10. An article ofmanufacture according to claim 5 further comprising at least onefiducial mark ink jet printed at at least one predetermined locationrelative to at least one area of colored material.
 11. A process forforming a front plane laminate having a color filter, which processcomprises: (a) providing a light-transmissive, electrically-conductivelayer; (b) applying a layer of an electro-optic material over thelight-transmissive, electrically-conductive layer; (c) ink jet printinga plurality of areas of colored material on to the layer ofelectro-optic material, the plurality of areas including areas of atleast two different colors; (d) applying a layer of a laminationadhesive over the layer of colored material; and (e) applying a releasesheet over the layer of lamination adhesive.
 12. A process according toclaim 11 wherein the colored material is ink jet printed in a fluidform, and is thereafter subjected to conditions effective to convert thefluid form to a solid form, thereby forming a coherent layer of thecolored material on the layer of electro-optic material.
 13. A processaccording to claim 12 wherein a first colored material is ink jetprinted in a fluid form, and is thereafter subjected to conditionseffective to convert the fluid form to a solid form, thereby forming acoherent layer of the first colored material, and thereafter a secondcolored material is ink jet printed on the layer of electro-opticmaterial.
 14. A process according to claim 11 further comprising ink jetprinting at least one fiducial mark on the layer of electro-opticmaterial at at least one predetermined location relative to at least onearea of colored material.